1.^2 TJic Aincrican Gcoloirist. Marcii, i8gh 
Grant," in 1894, describes the conglomerates on Grand 
Portage island, and places it at the base of the Keweenawan. 
Elftman,'" in 1895, describes the bedded and banded 
structure of the gabbro and an area of troctolyte. 
Winchell (N. H.)," in 1895, states that the eruptive rocks 
in Michigan, Wisconsin and Minnesota which have been in- 
cluded in the Keweenawan consist of two widely different 
series, of widely separated ages. The older of these series, the 
Norian, includes the great gabbro mass, augite syenites, the 
quartz-porphyries of the Great palisades and elsewhere along 
the Minnesota coast, and the anorthosytes. The more re- 
cent or Keweenawan proper includes the basal conglomerate 
at Grand Portage island, at Baptism river and at Duluth, and 
the later trap flows, some of which pass below the Norian 
rocks at the Great palisades. The "black rocks" in the Brule 
lake region are regarded as part of the Animikie slates. 
Van Hise," in 1893, 1895 and 1896, reviews and com- 
ments upon current pre-Cambrian literature. 
Winchell (N. H.),'* in 1897, discusses the nature and po- 
sition of the conglomerate in the Puckwunge valley. This 
conglomerate is correlated with that at Grand Portage island, 
Baptism river and Duluth. The unconformity below this con- 
glomerate separates the Norian from the Keweenawan. 
Winchell and Grant, '^^ in 1896, describe volcanic ash. 
2. Results of the Present Investigation. 
The preceding review of the literature upon the Keweena- 
wan of northeastern Minnesota shows the existence of a great 
diversity of opinions as to the proper subdivision of this series. 
All admit that several subdivisions are possible. Thus far no 
two geologists who have written concerning this area have 
agreed upon this point. The observations were confined 
largely to a narrow strip along the lake Superior coast and 
the northern half of the gabbro mass. Between these limits 
the region remained practically a "terra incognita." 
The writer, in 1893, began to map this formation for the 
Geological and Natural History Survey of Minnesota, and 
has devoted the greater part of five seasons of field study to 
this work. It soon became apparent that none of the suggest- 
ed subdivisions could be followed to any extent. Nearly all of 
